Why do i hate felling ill...

Some months ago my friends and I were planning to be in the beach for a weekend, we called others friends from other parts of Spain that  we have meet last year. We had to make a hard job to convince everyone to come. All was too perfect.... Then, the day before going all the people travelling went to eat a restaurant to celebrate the great weekend. The food was in bad state and we felt ill and we lost this perfect weekend.